1. Field of the Invention
The present invention relates to an imaging apparatus and a method for controlling the same. In particular, the present invention relates to a light emission control in a shooting operation with flashlight.
2. Description of the Related Art
In a conventional imaging apparatus, it is generally known that a shooting operation is performed with an auxiliary light source, such as an illumination device (e.g., a flashlight device), in a case where the luminance of a subject is insufficient (low). Further, there is a conventional technique capable of automatically controlling light emission of the auxiliary light source (e.g., the illumination device) according to shooting conditions (including subject luminance).
For example, a conventional technique discussed in Japanese Patent Application Laid-Open No. 2005-204120 takes the luminance of a subject into consideration when performing a gain (sensitivity) control of an imaging apparatus and an automatic light emission control of a flashlight device. Further, a conventional technique discussed in Japanese Patent Application Laid-Open No. 2005-181355 includes obtaining information relating to the depth of a subject (i.e., a subject distance) based on a range-finding result of a range-finding device having a plurality of range-finding points when a shooting operation with flashlight is performed and controlling the shutter speed in a flashlight shooting operation.
The technique discussed in Japanese Patent Application Laid-Open No. 2005-204120 includes setting a lower imaging gain when an image capturing operation is performed if the luminance of a subject is sufficiently bright. However, if the subject luminance becomes lower, the shutter speed may become slower than a predetermined value unless the imaging gain is increased. Therefore, the conventional technique includes increasing the imaging gain sufficiently to maintain the shutter speed at an appropriate level.
Further, the conventional technique includes performing a shooting operation with flashlight if the subject luminance becomes lower and a required imaging gain exceeds an upper-limit value. However, the exposure value realized by the shooting operation with flashlight is only appropriate for subjects that are positioned at the same distance.
Therefore, according to the technique discussed in Japanese Patent Application Laid-Open No. 2005-204120, in a case where a flashlight shooting operation is performed for two or more subjects that are different in subject distance and are simultaneously present in an image-capturing screen, if the light emission amount is controlled to provisionally realize an appropriate exposure for a subject positioned on the near side, the light quantity for a subject positioned on the far side will be insufficient.
Further, in a case where there is a large difference between the background light and the flashlight in color temperature, the near side subject is prioritized in the white balance control and therefore an image of the far side subject may become darker with unnatural color reproduction. In short, obtaining an adequate image for each of all subjects that are different in subject distance is difficult.
Hence, the technique discussed in Japanese Patent Application Laid-Open No. 2005-181355 proposes to set a slower shutter speed in a shooting operation with flashlight if it is determined that the subject depth is larger compared to a case where it is determined that the subject depth is smaller, based on the range-finding result of the range-finding device having a plurality of range-finding points. The above-described setting is effective to reduce the darkness of a subject positioned on the far side because the exposure amount by the background light can be increased.
However, generally for the purpose of reducing camera shake, a lower limit is set for the shutter speed in the flashlight shooting operation. If the shutter speed is set to a lower value, it will be difficult to obtain an image free from blur.